The Australian state of New South Wales recorded zero new locally acquired Covid-19 cases in the 24 hours to 8pm on Saturday from more than 18,000 tests.
There were an additional six cases in returned travellers in hotel quarantine.
NSW Health said on Sunday it remained unsure how an infected east Sydney man caught the virus, which shared the same genomic sequencing as a returned traveller from the United States in quarantine.
The man aged in his 50s subsequently infected his wife, but no other close contacts to date.
As a result, the NSW government has extended its current Covid-19 restrictions for another week, except for mask usage in retail settings.
Retail customers are no longer obliged to wear masks, but staff must do so.
Household gatherings remain capped at 20 people, mask usage remains mandatory on public transport and indoor venues such as theatres and aged care homes, and singing and dancing remains mostly banned.
Hospitality patrons are still not permitted to drink while standing.
"NSW Health thanks the community for their strong response to calls for testing and continue to urge everyone in NSW with even the mildest symptoms - such as cough, headache, fatigue, sore throat or runny nose - to come forward immediately for testing, then isolate until you receive a negative result," Dr Stephen Conaty said in a statement on Sunday.
"High testing rates are vital for detecting any unidentified chains of transmission in the community."
One Covid-19 patient in NSW is currently in intensive care and on a ventilator.
Almost 780,000 vaccinations in total have been administered in NSW, which includes those overseen by the Commonwealth.
Sydneysiders were this week urged to wear masks and adhere to other restrictions without cancelling their Mother's Day plans.
Liquor and Gaming NSW on Saturday also urged businesses to do the right thing over the weekend, with compliance officers out in force on Sunday.
Businesses can be fined up to $A5000 ($NZ5300) and forced to shut their doors for defying Covid rules, including the requirement all patrons check in.
TRANSTASMAN BUBBLE
New Zealand will lift its partial suspension of a "travel bubble" with Australia from 11:59pm on Sunday.
It had blocked travel to and from NSW, Australia's most populous state, on Thursday after a couple in Sydney with no links to high risk professions or people tested positive for Covid-19.
New Zealand's Covid-19 Response Minister Chris Hipkins said travel to and from NSW, home to one-third of Australia's 25 million population, would resume after health officials determined that the risk to New Zealand was low.
"New Zealand has consistently taken a precautionary approach to keeping COVID-19 out," Hipkins said in a statement.
Australia and New Zealand began allowing quarantine-free travel less than a month ago, after a protracted run of zero locally-acquired cases in the neighbouring countries.
"Border controls are a key tool for stopping the introduction and spread of new cases from overseas and remain central to our elimination strategy," Hipkins said.
Australia has meanwhile barred travel from India due to high infection rates, but it has said it would begin chartering repatriation flights on May 15.
- AAP and Reuters
